Due to its high prevalence and its ability to cause severe disease in humans for which treatments are unavailable, West Nile (WN) virus has become an important public health concern in the U.S. The unmet medical need of developing effective WN virus therapeutics has been recognized by NIAID, which includes several flaviviruses in its current list of category A-C pathogens. [unreadable] The long-term objective of this project is to develop a small molecule therapeutic to treat severe West Nile (WN) virus infections in humans. The specific goal of this study is to identify small molecule inhibitors of WN virus by high throughput screening (HTS) and select among them lead compounds for future drug development. To this end, we have developed an in vitro WN virus infection assay using wild type virus and a human cell line. This assay was adapted to high-throughput format and was used to screen a small library of compounds from which three previously unknown WN virus inhibitors were identified. The Phase I project will expand this repertoire by screening additional compound libraries. `Screening hits' will then be critically evaluated for potency, selectivity, cytotoxicity and `druggability' in order to select lead candidates for detailed drug characterizations in Phase II studies. [unreadable] Successful development of a small molecule therapeutic for WN virus infections should provide the basis for similar therapeutics to treat other flavivirus infections of wider global importance, such as dengue fever. [unreadable] [unreadable] West Nile (WN) virus causes severe illness in the elderly and people with compromised immune systems. The virus is transmitted by mosquitoes and is widespread in the USA. There is no proven treatment available. This research will identify small molecule drugs to treat illness caused by WN virus infections in humans. [unreadable] [unreadable] [unreadable]